The name MF/HF/VHF etc were defined by ITU v.431 originally in 1953. Amateur radio operators in the 1950s commonly were using “shortwave” frequencies (now referenced as HF commonly). As it’s been told to me from multiple operators in that era, the naming scheme used by ITU for each group is based on the amount of bandwidth available in each group, not based on any presumption of AM radio broadcasts being used as a baseline.